We started in this construction business back in
the late 70's and one thing that continues to run rampant in the
world of heating is the treatment of radiant systems as popular
science experiments. This happens despite decades of research
and the existence of design and installation standards.

Presented
here are the six most common mistakes we've come across in our
years of helping people figure out why their
homemade system
isn't working...all of them relate to the interface
between HVAC systems and the building enclosure. Ignore them at
your own risk.

Some people may wonder why are there ducts in a
radiant system. Well the radiant takes care of the
comfort quality. You still need to take care of the
air quality ergo the ducts. Our first choice is a
dedicated outdoor air systems. Since these systems only have
to deal with ventilation air they are small, effective and
efficient.

Click to enlarge

This is a simplified schematic for an energy
efficient radiant based HVAC system using radiant floor heating
and an HRV. In a high performance home under 3000 sf this system
would fit into a space equivalent to a three piece bathroom.
Example below.

How to avoid stepping on
radiant heating and cooling landmines - Six common
mistakes and how to avoid them. Copyright (C) 2009, Robert
Bean, R.E.T., P.L. (Eng.)

Landmine #2 - happens when
radiant cooled and heated floors are not thermally
decoupled from return air plenums. This results in
parasitic heat transfer between the floor and duct
leading to loss of control over the air system.

Solution: insulate between radiant systems and return
air plenums.

Landmine #3 - happens when
radiant cooled and heated floors and distribution piping
is not thermally decoupled from
supply air ducts. This
results in parasitic heat transfer between the floor,
pipes and ducts leading to loss of control over the air
system.

Solution: insulate between
radiant systems, piping and supply air ducts.

Landmine #4 - happens when
radiant cooled and heated floors are not thermally
decoupled from domestic plumbing lines. This results in
parasitic heat transfer between the floor and pipes
leading to loss of control of plumbing water
temperatures.

Landmine #5 - happens when
radiant cooled and heated floors are not thermally
decoupled from the exterior elements. This results in
parasitic heat transfer between the floor and outside
leading to energy inefficiencies and discomfort.

Solution: seal and
insulate between radiant systems
and exterior enclosures.

Landmine #6 - happens when
radiant cooled and heated floors are not thermally
decoupled from the exterior elements through
cantilevered sections. This results in parasitic heat
transfer between the floor and outside leading to energy
inefficiencies and discomfort.

Solution: seal and
insulate between radiant systems
and exterior enclosures.